The present invention relates to a transmission comprising a belt passing over pulleys and composed of a stack of blocks working in compression and supported by one or more bands.
A transmission of this type is usually a variable ratio transmission. For this purpose the inner face of the cheeks of each pulley is conical, and these cheeks can be moved axially towards and away from one another. The blocks have a trapezoidal shape complementary to that of the conical surfaces of the pulley cheeks. Thus, when the pulley cheeks are noved towards and away from one another the blocks rise or fall radially along the cheeks while remaining in continuous contact with them, thus providing a transmission ratio which is variable in dependence on the ratio of the mean radii on which the blocks are working on the two pulleys.
As a rule, in such a transmission, the blocks are of sheet iron and the bands are made of steel. The entire device is lubricated.
The object of the present invention is to provide a belt and pulley transmission of the kind indicated above, in which the conditions of assembly and operation are improved and which can work without lubrication.